As to an ink-jet image forming method, high-resolution images are possible to be recorded by a relatively simple apparatus, and the ink-jet image forming method has been rapidly in progress in various fields. There are a wide range of applications to use the ink-jet image forming method, and a recording medium or ink suitable for each purpose is employed. Specifically, in recent years, recording speed has been largely increased, and printers each having convenience printing-strength properties have been developed.
In the case of this ink-jet recording system, ink is ejected from an ink-jet head, and deposited onto a recording medium to form images. The ink should exhibit a condition of low viscosity in order to eject the ink from the ink-jet head. On the other hand, high viscosity ink is demanded in order to prevent color mixing called bleed generated when plural kinds of liquid-droplet ink each exhibiting different hue are deposited on the recording medium.
As a method of solve this dilemma, a UV radiation curable type ink-jet recording method employing actinic energy radiation curable ink is practically utilized. This is a technique by which an actinic energy radiation curable monomer and a photo-initiator are contained in ink, and the resulting one is exposed to actinic energy radiation, for example, UV radiation after depositing it onto a recording medium to cure the ink, resulting in achievement of a good balance between acquisition of an ejection property and prevention of bleed.
On the other hand, as a technique to suppress bleed, there is an image forming method employing so-called hot-melt ink wherein the hot-melt ink is present at ambient temperature as a solid phase, but is present at a high operation temperature of an ink-jet printing apparatus as a liquid phase (refer to Patent Document 1, for example).
In the case of this hot-melt ink system, when depositing ink-droplets on the surface of a recording material, they are rapidly solidified with no expansion of the recording material in the direction of the area, whereby high resolution images can be formed. Since actinic energy radiation curable ink as well as hot-melt ink does not contain a solvent in an ink component, it is advantageous that images can be formed on a recording material exhibiting no ink absorption. In addition, disclosed is a technique by which a gelation action-producing material is contained in an actinic energy radiation curable ink component via temperature change in order to improve dot gain and glossiness, and images are formed via the temperature change and exposure to actinic energy radiation after ink ejected from an ink head is deposited on a recording material.
Though the inventors surely confirmed that a certain amount of an improving effect to the dot gain and the glossiness was observed via application of the above-described technique, it was found out that the improving effect was insufficient, resulting in insufficient characteristics to printing durability, print-through resistance, paper-feeding suitability and offset resistance.